Cascading Style Sheets

Cascading Style Sheets (or CSS) makes web page design a lot more flexible and more interesting than just HTML.

With plain HTML you define the colors, text sizes and tables throughout your web pages.  If you want to change a certain element you have to work your way through the document and change it.

With CSS you define your web pages' colours and sizes in styles.  Within your web documents you refer to these styles.  Should you change the definition of a style, that will change the look of your entire site.  That makes web design much more convenient and changes more efficient.

Another big advantage is that CSS offers detailed attributes than plain HTML for defining the look and feel of your site.  Visual elements can be more precisely placed on the screen.

Finally, the CSS styles can be written to a separate file so the user will only need to download it once - in the external style sheet document. When surfing the rest of your site, the CSS file will be cached on the user's computer, and consequently speed up web page access time.

from www.echoecho.com